Note on Technical Library and
Appendices

During Cohen’s years with the Delaware State Planning
Office (1967-1971), he created a library classification system for planning
related materials including reports, pamphlets, studies, books, periodicals,
and other materials useful for research.Modeled on a cataloging system used at the Fels Institute at the University of Pennsylvania, Cohen’s creation was
easily adaptable for use in any planning office.Each document was given a three digit call
number designating its major category, sub-category, and regional
classification.Within the categories,
items were then giving a sequential number.In addition to a call number, materials were also given a volume or
report number as well as a year.